Book of Extended Summoning

Wondrous item, uncommon (requires attunement)

This leather-bound book is inscribed with runes relating to conjuration magic, enhancing the user’s spells that summon creatures to serve them. Any conjure animals, conjure celestial, conjure elemental, conjure fey, conjure minor elementals, conjure woodland beings, or similar spell (GM’s discretion) you cast has a duration of “Concentration, up to 2 hours.” In addition, you have advantage on Constitution saving throws made to maintain concentration on such spells.